The present invention relates generally to valves and more specifically to an improved valve seat retention structure.
The valve generally includes a housing, a movable valve element and a valve seat. The valve seat is secured to the housing by various means depending upon the size of the valve and the type of valve. Butterfly valves, since they do not engage the valve seat except in the closed position, are easier to design retention structures than for other types of valves, for example, ball and gate valves, wherein the valve element continuously engages portions of the valve seat in movement between its open and closed positions. With gate valves having metal valve seats, these seats are generally an integral part of the housing. In other environments where rubber or elastomeric material may be used to form the valve seat, the top of the valve seat is held within an annular recess at its top by the gate itself and a lug or other retaining element is welded at the bottom of the seat. In smaller sized valves, for example, the 30 inch valve, this type of retention system has proven satisfactory whereas in the larger valves such as 72 inches, the number of welded retainers that must be included makes replacement of the valve element difficult. Also, the elastomeric material may be bonded to the annular recess and this bonding also makes replacement difficult.
Thus, there exists the need for a valve retention system which makes valve seat replacement relatively easy.
An object of the present invention is to provide a valve seat retention system which makes valve replacement quick and efficient.
Another object of the present invention is to provide a valve seat retention system for use in large valves.
A further object of the present invention is to provide an improved valve retention system for gate valves.
These and other objects of the invention are attained by forming the inner wall of an annular recess for the valve seat sufficiently thin to be deformed at portions thereof to engage at least portions of a lateral surface of the valve seat to thereby retain the valve seat in the annular recess. The annular wall of the valve seat which is engaged by the deformed portions of the inner wall of the recess forms an acute angle with the base surface of the valve seat. Thus, the top edge of the deformed portion of the inner wall extends into the recess radially beyond the adjacent lateral edge of the base surface of the valve seat to produce the retention. The valve seat is easily replaced by unbending the deformed portions and removing the annular valve seat. The retention system is designed specifically for gate valves, but may also be used for other types of valves.